k1 = {1:1, 2:2}.items()
k2 = {1:1, 2:2, 3:3}.items()
k3 = {4:4}.items()

___assertEqual(k1 - k2, set())
___assertEqual(k1 - k3, {(1,1), (2,2)})
___assertEqual(k2 - k1, {(3,3)})
___assertEqual(k3 - k1, {(4,4)})
___assertEqual(k1 & k2, {(1,1), (2,2)})
___assertEqual(k1 & k3, set())
___assertEqual(k1 | k2, {(1,1), (2,2), (3,3)})
___assertEqual(k1 ^ k2, {(3,3)})
___assertEqual(k1 ^ k3, {(1,1), (2,2), (4,4)})
